Weather in Chicago in December

The month to avoid. Of the twelve, December is the one to avoid. Highs sit at 2.6 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

December ranks 10 of 12 — near the bottom of Chicago's year. September is the month that works, and the swing between the two is 53 points, which is a different holiday rather than a slightly better one.

Rain on 9 days, 2 of them heavy. Enough to need a plan B, not enough to need a plan around it. Layers, and a genuinely waterproof outer — at 2.6 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: 19 nights fall below freezing; the day barely swings — 4.4 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 16.4 °C and the coldest night fell to -18.5 °C, and the wettest single day dropped 42 mm — roughly 72% of the month's rain in one day.

December is moderately variable: 11 mm in the driest year against 133 mm in the wettest, around an average of 58 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind sits around 20.2 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 85%, which at 2.6 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How December sits in the year

The month is on the way down: 6 °C cooler than November, with January dropping another 2.8 °C. The first week and the last are not the same trip.

Daylight in December

December sits at the dark end of Chicago's year — 9.2 hours of daylight against 15.2 at midsummer, holding steady all month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

An inland climate

With no coast nearby, the year swings a fair way — 30.2 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

December in Chicago versus nearby

If Chicago is one option among several, the nearby comparison is worth making. Milwaukee is close enough to be a coin toss — 2.1 °C cooler, 2 days less rain. Grand Rapids is the weaker option in December — within a degree on temperature, 3 days more rain.

So: December is a compromise. September is 51 points better and is what Chicago is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Chicago

See all twelve months in Chicago, or where else to go in December.